In an image forming apparatus, such as a copier, a printer, or a facsimile, that forms an image on a paper sheet by the electrophotography, a sheet feed cassette for storing paper sheets is provided so as to be attachable/detachable to the apparatus main body. Here, a configuration of a conventional sheet feed cassette is described in the following with reference to FIGS. 8 through 11.
FIG. 8 is a perspective view of the conventional sheet feed cassette. FIG. 9 is a perspective view of a side cursor, and its peripheral, of the sheet feed cassette. FIG. 10 is a perspective view of an end cursor, and its peripheral, of the sheet feed cassette. FIG. 11 is a perspective view of the end cursor.
As shown in FIG. 8, a sheet feed cassette 105 includes a cassette main body 105A that is in the shape of a flat rectangular box whose top is opened. The sheet feed cassette 105 includes a paper sheet mounting plate 107, a pair of side cursors 108, and an end cursor 109. The paper sheet mounting plate 107 can sway about a fulcrum 107a. The pair of side cursors 108 can be slid so as to abut on opposite sides of the paper sheets mounted on the paper sheet mounting plate 107 and align the width of the paper sheets. The end cursor 109 can be slid so as to abut on the rear end of the paper sheets and align the front and rear ends of the paper sheets.
As shown in FIG. 9, the pair of side cursors 108 are respectively provided with claw portions (not shown) that have protruding-and-recessed surfaces so as to be engaged with racks 111 that are formed along the slide direction of the side cursors 108. When a knob member 110 is picked and pressed, the engagement between the claw portions and the racks 111 is disengaged and the pair of side cursors 108 are slid by the same amount in opposite directions along the paper sheet width direction by a rack and pinion mechanism (not shown). Subsequently, when the force pressing the knob member 110 is released, the claw portions are engaged with the racks 111 again and the sliding of the side cursor 108 is locked, and the side cursors 108 is fixed at that position.
In addition, as shown in FIG. 11, knob members 112 that can be elastically deformed are integrally formed with the end cursor 109 respectively at the left and right ends thereof. Claw portions 112a having projecting-and-recessed surfaces are respectively formed at lower ends of the knob members 112. As shown in FIG. 10, on the bottom surface of the cassette main body 105A, a guide groove 116 is formed along the slide direction of the end cursor 108. Furthermore, racks 117 extending in the slide direction of the end cursor 109 are formed in parallel with each other on both sides of the guide groove 116.
A guide projection 109a which is integrally formed with the end cursor 109 is fitted in the guide groove 116, and the claw portions 112a formed on the knob members 112 at the left and right sides of the end cursor 109 are engaged with the racks 117 on the left and right sides, respectively. When the knob members 112 on the left and right sides are picked and pressed inward, the knob members 112 are bent inward, and the engagement between the claw portions 112a under the knob members 112 and the racks 117 is disengaged. This allows the end cursor 109 to slide along the guide groove 116. Subsequently, when the force pressing the knob members 112 is released, the claw portions 112a are engaged with the racks 117 again and the sliding of the end cursor 109 is locked, and the end cursor 109 is fixed at that position.
Meanwhile, there is known a configuration of a sheet feed cassette where the side cursors and the end cursor are provided in an attachable/detachable manner, and the attachment positions thereof can be replaced with each other. In addition, in this configuration, when tab sheets are stored in the sheet feed cassette, both sides of the tab sheets are supported by the end cursor and one side cursor, and the rear end of the tab sheets is supported by the other side cursor (see Patent Literature 1). With this configuration, in both cases of tab sheets and normal paper sheets, it is possible to store the sheets in the state where the rear end of the sheets is aligned, without attaching and/or detaching any other member.
Furthermore, with regard to an image forming apparatus that includes: a sheet feed cassette having an end cursor; and a sheet feed roller unit that is supported by a drive shaft which extends perpendicular to the sheet feed direction, there is known a configuration where the sheet feed roller unit is supported at a position closer to one side of the drive shaft than the center of the drive shaft, and the end cursor includes an expanded portion that has been expanded toward the other side of the drive shaft (see Patent Literature 2). With this configuration, it is possible to prevent skewing of a paper sheet in the earlier stage of the sheet feed in the sheet feed cassette.